1. Field of the Invention
The present invention relates generally to display of digital image data.
2. Description of the Related Art
Contrast within an image, such as that captured by a digital camera, can often need improvement. If the image has insufficient contrast, features and details of the image may be indistinguishable from other portions of the image. Therefore, evaluation and adjustment of the image contrast may be useful prior to display.
One method for evaluating the contrast of the image includes generating a histogram table for the image. The histogram table represents a frequency of occurrence of each pixel value within the image. Therefore, evaluation of the histogram table can identify similar pixel values that occur with sufficient frequency in the image such that contrast is adversely affected. Using the information gleaned from the histogram table, the image can be appropriately refined to improve contrast prior to display.
Conventionally, data defining both the image and the associated histogram table is stored in a random access memory (RAM). Histogram circuitry is used to compute the histogram table for the incoming image and store the histogram table in the RAM. For each incoming pixel defining the image, the histogram circuitry of the prior art first operates to determine a value of the pixel. Using the determined pixel value as an address into the histogram table, the histogram circuitry of the prior art then reads a tally value corresponding to the pixel from the histogram table in the RAM. The histogram circuitry of the prior art then operates to increment the tally value by one. Then, the histogram circuitry of the prior art writes the incremented tally value for the pixel back to the histogram table in the RAM. Thus, for each incoming pixel, the histogram circuitry of the prior art performs a read operation from the RAM, an increment operation, and a write operation to the RAM. Performing the read and write operations for each incoming pixel to generate the histogram table utilizes a large amount of available RAM bandwidth. Therefore, the conventional histogram circuitry both reduces the amount of RAM bandwidth available for other processes and consumes a large amount of power. Furthermore, increased power consumption can be particularly problematic in mobile electronic devices where power is generally at a premium.
In view of the foregoing, there is a need for an improved histogram table generation system that requires less RAM bandwidth and less power consumption.